Antimicrobial Drug Sensitivity Testing
Antimicrobial Drug Sensitivity Testing
Antimicrobial Sensitivity Testing
Introduction
Antimicrobial sensitivity testing is important clinically because the proper selection of an antimicrobial drug in the treatment of a bacterial infection is ideally based on the knowledge of the sensitivities of the infecting organism. In this laboratory exercise you will be working within a group performing a commonly used test that is designed to determine whether or not an isolated organism is able to be treated using a specific antimicrobial drug. The procedure is called sensitivity testing. This testing method allows clinicians to obtain information needed in order to make an informed and concise decision in reference to the antimicrobial drug usage.
Methods and Materials
Materials being used in this test include:
6 Mueller-Hinton agar plates
14 cartridges of antimicrobial drugs
three automatic dispensers
two 1mL pipettes and pipette pump
broth culture of Staphylococcus aureus and Escherichia coli
spreading rod soaking in ethanol
two forceps soaking in ethanol
marking pen
ruler
antimicrobial sensitivity chart
To start off this lab you will
Label the plates with the name of the organisms (three plates per organism)
Create a bacterial lawn by
Inoculate each dish with 0.2mL of the appropriate bacteria. Deposit the inoculum in the center of the plate.
Remove the spreading rod from the ethanol and ignite the ethanol (Do not leave the rod in the Bunsen burner flame longer than is needed to ignite the ethanol.) Allow the ethanol to burn off. Spread the culture over the entire surface of the plate using the sterilized spreading rod. Before continuing wait five minutes to allow the culture to be absorbed by the nutrient agar.
Apply antimicrobial disks to the plate using the dispensers as demonstrated by your instructor. Gently press the disks to the surface of the agar with a sterile set of forceps.
Incubate the Petri dishes for at least 24 hours at 37 degrees Celsius.
Measure the diameter (in mm’s) of region around the disks where growth was inhibited. This region will appear as